Tube support



Jan. 2, 1968 R. 'r. MATHEWS 3,361,197

TUBE SUPPORT Filed Feb. 5, 1966 6 Sheets-Sheet 2 INVENTOR RALPH T. MATH EW S BY a/wigwemi ATTORNEY Jan. 2, 1968 R. "r. MATHEWS 3,361,197

TUBE SUPPORT Filed Feb. 5, 1966 6 Sheets-Sheet 3 RALPH T. MATHEWS BY 3 M5 ATTORNEY TUBE SUPPORT s Sheets-Shec 4 FiledFeb. .5, 1966 INVENTOR RALPH T. MATHEWS J o 'f/ 4 W F w L ATTORNEY Jan. 2, 1968 RlTMATH'Ews 3,361,197

TUBE SUPPORT Filed Feb. 5, 1966 e Sheets-Sheet 5 FIGS v I'-- Y INVENTOR I O RALPH T. MATHEWS 7 Fig.6 \MI BY 'Wwy}7w% ATTORNEY Jan. 2, 1968 R. 'T. MATHEWS TUB E SUPPORT Filed Feb.

6 Sheets-Sheet 6 I. INVENTOR \\\\\\\\\\a 46 RALPH II MATHEWS ATTORNEY United States Patent Oflfice 3,361,197 Patented Jan. 2, 1968 3,361,197 TUBE SUPPORT Ralph T. Mathews, Wallingford, Pa., assignor to E. I. du Pout de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed Feb. 3, 1966, Ser. No. 524,811 4 Claims. (Cl. 165-162) ABSTRACT OF THE DISCLOSURE A demountable tube support strap bent in a repetitive undulatory pattern intermediate the ends, particularly intended for the firm support of individual rows of the finned tubes of air-type heat exchangers having a lengthto-diameter ratio above about 200.

As taught in my copending patent application S.N. 524,- 712, filed of even date and of common assignment herewith, I have invented an air-type heat exchanger employing finned tubes arranged in a pair of separate bundle subassemblies oriented in upright V disposition, with the finned tubes carried in generally horizontal superposed planes, although the tubes can optionally be inclined progressively in flow path sequence to insure gravity drainage of process liquid therethrough. The finned tubes are preferably utilized in long lengths such that the length-todiameter ratio is in excess of about 200, and a serious problem of tube support therefore exists over the lengths of the tube bundles, especially when the tubes are full of heavy process liquids.

This invention consists of a light-weight, low cost demountable support strap for heat exchangers of the design cross-referenced, which strap confers a cross-bracing to the heat exchanger tubes, tying them into a rigid pattern preserving uniform air-throughput passages within the bundles, even in environments where heavy vibrations are transmitted from neighboring equipment. At the same time the tubes are arrayed in an invariant pattern permitting deep and uniform penetration of water droplets supplied by supplementary cooling water sprays, which is sometimes necessary to obtain the full benefits of air-type heat exchange.

The manner in which the foregoing is accomplished will be clear from the following detailed description and the drawings, in which:

FIG. 1 is a plan view of an assembled manifold type tube bundle,

FIG. 2 is a section taken on line 2-2, FIG. 1,

FIG. 3A is a fragmentary end view of the tube bundle of FIGS. 1 and 2,

FIG. 3B is a fragmentary cross-sectional end view of a tube bundle such as that shown in FIG. 3A, except that this bundle is provided with box headers,

FIG. 4 is a fragmentary cross-section of a tube bundle showing details of a preferred support strap construction and assembly with respect to the finned tubes supported thereby,

FIG. 5 is a fragmentary perspective view showing a convenient way of assembling tube bundles utilizing the tube support of this invention,

FIG. 6 is a fragmentary perspective view of an alternate design of tube support according to this invention adapted to longitudinal tension assembly within the tube framework,

FIG. 7 is an end view taken on line 7-7, FIG. 6,

FIG. 8 is a side elevation view of a special design of tube support employed as a temporary aid in the assembly of finned tubes within bundles,

FIG. 9 is a plan view of a U-shaped individual transverse tube support member shown in assembled relationship with the tube support of FIG. 8, and

FIGS. 10 and 11 illustrate a finned tube assembly technique readily performed with the aid of the tube support of FIG. 8.

Generally, the tube support of this invention consists of the following: in an air-type heat exchanger comprising a rigid external framework, inlet and outlet process fluid headers connected at opposite ends in the process fluid flow path with a tube bundle disposed in inclined relationship with respect to the horizontal, the tube bundle being made up of a multiplicity of finned tubes having a lengthto-diameter ratio above about 200, the tubes being disposed in generally horizontal superposed planes, tube support means carrying substantially the full weight of the tubes individually disposed longitudinally between the inlet header and the outlet header generally transverse rows of the tubes lying in a common substantially horizontal plane within the tube bundles, the tube support means consisting of a unitary strap bent in a repetitive undulatory pattern intermediate the ends to provide a succession of shallow arcuate concavities abutting the peripheries of the finned tubes, and support members fixedly attached to the framework receiving the ends of the straps in weight-supporting relationship.

Referring to FIGS. 1 and 2, there is shown an assembled tube bundle consisting of an enclosing structural steel framework denoted generally at 12, made up of longitudinal channels 47 bolted to heavy transverse and I-beams 48 and somewhat lighter intermediate transverse I-beams 49. At the left-hand end are a process fluid supply header 38 and a process fluid discharge header 39 supported within yoke openings 51a cut into the ends of yoke plates 51, which latter are bolted or welded in parallel alignmen-t with and to the web portions of channels 47, but with header-supporting ends extending outboard therefrom.

It will be understood that the tube bundles comprises a multiplicity of relatively long (typically 36) straight lengths of finned tubing 33, the outer finned tube jacket portion of which can be of unitary construction consisting of an aluminum tube provided with a continuous helical screw configuration external fin. This jacket is pressed tightly over a concentric inner tube fabricated from stainless steel or the like, resistant to corrosion by the process fluid transported therethrough and also sufficiently strong to withstand the process pressures and temperatures. In a typical construction the outside fin diameter is 2.25" with a pitch providing seven to nine fins per inch of tube length for an inside process tube of 1" outside diameter. The fin tube can typically be approximately 0.040 wall thickness, while individual fins can have a crest thickness of 0.014" and a root thickness of 0.050".

The heat exchanger of FIGS. 1 and 2 is of the high pressure manifold type, utilizing four-pass serpentine flow from process fluid inlet header 38, through the finned tubes 33, to process fluid outlet header 39.

Thus, it will be understood that a single tube bundle such as that shown in FIG. 1 is built up from a multiplicity of parallelly disposed individual fin tube sub-assemblies, the straight length ends of which are connected in process fluid flow continuation by U-bends 40, welded or otherwise fixedly attached thereto at joints 41. Arcuately cut-away end plates 30 seal the bundles against by-pass flow of air from the ends of the bundles, the desired flow of air being transverse the finned tubes as indicated by the directional arrows. Connection is made to headers 38 and 39 via enlargements 42 at the tube ends, which are weld-attached in open communication with the headers disposed in parallel one with the other but transverse the tube bundle.

With lengths of finned tubing 33 as long as described, it is imperative that the weight of the tubes be supported at frequent intervals along their lengths. Otherwise the tubes of the bundle will sag in random fashion, thereby preventing all uniformity in air passage through the bundle, as well as any uniform ingress of cooling liquid sprayed on the outsides of the fins. Moreover, since individual finned tubes 33 sometimes require that maintenance work be done on them, tube weight-supporting means should preferably be readily demountable to permit ready access to any point in the interior of the tube bundle by temporarily displacing adjacent tubes laterally so as to expose any particular one for repairs without the necessity of removing more neighboring tubes than is absolutely necessary.

Tube support in this invention is provided by demountable support straps 46, shown in plan in FIG. 2 and in end elevation in FIGS. 3A and 3B. These can typically be fabricated from aluminum 2" x 12%" x thick having their intermediate lengths bent into a regular repetitive undulatory pattern to form concave recesses conforming quite closely to the peripheral expanses of finned tubes 33. The pitch of the undulations is such that neighboring finned tubes 33 in any given row are spaced one from another at equal pitches of typically 2 /2" for the specific tubes of 2 /4 outside diameter hereinbefore mentioned, thus leaving a longitudinal A air passage clearance between adjacent tubes of any given horizontal row. A small clearance of typically is provided between the tops of the finned tubes 33 and the undersides of the support straps for the next succeeding row thereabove, which accommodates some lack of straightness in adjacent tubes; however, tubes 33 are snugly brought up into fixed spotted relationship by the springiness of individual tubes and support straps, locking the tubes in a tight uniform tube center-to-tube center equilateral triangular pattern throughout as denoted at g in FIG. 4.

The ends of straps 46 fit slidably into slots 60 cut into channels 50, fixedly attached to I-beams 49 by bolts,

clamps or other conventional means with channel webs disposed inwardly towards the finned tubes 33. One satisfactory method is to utilize right angle clips 61 (FIG. 5) arranged in opposition in confrontation with the flanges of channel 50 with lower legs of the clips abutting the undersides of the adjacent flanges of I-beams 49. Clips 61 and the channel 50 flanges are drilled in line to accommodate a through bolt 61, threaded at each end to receive locking nuts 63.

Aluminum can be used as the material of construction for channels 50; however, in this case it is desirable to isolate the channels from direct contact with steel structural members, such as the I-beams 49, and this is accomplished by interposing a barrier strip (not shown) of micarta or equivalent material between the abutting members.

The weight of finned tubes 33 carried by support straps 46 is transmitted through channels 50 to the rigid heavy structural steel bundle framework 12 without sagging of the finned tubes or any misalignment therefrom out of the precise placement tube pattern it is essential to maintain in order to obtain optimum cooling air transit transverse the tubes of a bundle in lines generally parallel to the webs of channels 47 (refer FIG. 2).

Referring particularly to FIG. 4, a preferred design of support strap 46 has the concave recesses formed on a circular arc conforming quite closely to approximately 60 of the lowermost peripheral expanse of finned tubes 33. The rigorous development of this design is depicted schematically in broken line representation for one of the straps, wherein the longitudinal center lines are depicted for the straight strap ends and a construction line is drawn from the center line at the left-hand side, where the strap is first bent arcuately, to the center line at the right-hand side where the straight strap end occurs again. This construction line makes its smallest included angles with the strap end center lines of magnitudes of about 150.

It will be understood, of course, that the degree of wrap-around of straps 46 with respect to finned tubes 33 can vary throughout a range of from about 15 to about 75 of peripheral contact measured from the finned tube centers, depending upon the degree of direct support application which is desired.

An alternate design of undulated support strap length can employ a sinusoidal pattern to develop the concavities, contact between straps and finned tube exteriors then being much more limited in area extent. In general, it is preferred that the peripheries of the finned tubes 33 not extend more than approximately 25% of a finned tube external radius within the concavities of the strap undulations for this design, which affords very adequate locational fixation of the tubes of the assembled bundle while still retaining the advantages of ready dernountability hereinafter discussed.

In some installations it is preferred to support the tubes by abutment against rings fixed concentrically on the base tubing from which certain of the fins are left out so as to accommodate the rings and, of course, the tube support means of this invention is then equally well-suited to employment with the rings.

The convenience in assembly of my support straps is portrayed in FIG. 5, which illustrates how successive tube layers can be readily built up in sequence between pairs of adjacent support straps 46.

It is usually preferred to assemble the tubes in a bundle by bringing them into place from the top, and this is most easily done by laying the bundle framework fiat before attachment thereto of the uppermost I-beam 49, channel 50 sub-assembly, denoted generally at F in FIG. 5. The lower ends of the straps are then inserted in order from right to left within slots in the bottom channel 50, successive finned tubes 33 being next placed one above the other in each row, cradled within the opposed undulations of adjacent straps, after which the next rows in horizontal progression to the left are built up in turn. As shown in FIG. 5, the extreme right-hand strap, denoted 46', is actually only a half-strap, retained at its end abutting channel 47 by welded clips 67, the purpose being to utilize to the utmost all available cross-sectional area within the bundle framework for the accommodation of heat exchange tubes. Any unused open area is closed off by spring-clipped panels 68 (FIG. 3A), which thus prevents bypass of air through the unit.

Usually, the weights of tubes 33 bias straps 46 rightwardly as seen in FIG. 5, so that there is automatic alignment of the straps in their proper final positions; however, if desired, a rake tooth retainer (not shown) can be used to temporarily secure the straps against lateral displacement one from another.

An exceptionally convenient temporary retainer is that detailed in FIG. 5, straps 46 being in this instance provided with slots 66 at their upper ends deep enough for full reception of tension bar 69, which is advanced in notch-by-notch progression from right to left. The lefthand end of bar 69 is formed into a hook 70 adapted to overlie the bottom of slot 66 in the left-most strap 46 and thereby lock all tube rows to the right against any lateral shifting during the time that the tube handle is being assembled.

The top edge of tension bar 69 is provided with a succession of equally spaced notches 71 located distances apart equal to the final desired spacing of individual straps 46 one from another. A slot 72 large enough to slidably receive tension bar 69 is cut in longitudinal channel 47 at the points where support straps 46 are employed, and there is slipped over the right-hand free end of the bar a freely slidable slotted keeper piece 73 which drops by force of gravity into sucessive notches 71 on bar 69 during its advance to the left, securely locking all straps in place at appropriate staged spacings until another notch advance is desired. When all finned tubes 33 have been assembled within the bundle, sub-assembly F can be lowered into place to an extent where the upper ends of straps 46 just enter top slots 60, which position can be temporarily preserved by utilizing a U-shaped locking dowel inserted through holes 75 drilled in the web of channel 47. Then tension bar 69 can be rocked slightly to disengage hook 70 and the bar withdrawn completely through slot 72, after which the sub-assembly F is lowered to final position with upper ends of straps 46 fully inserted within slots 60. Finally, sub-assembly F is bolted securely at both ends 49a to the longitudinal channels 47 and the tube bundle assembly is complete.

An alternate, somewhat simplified design for retention of support straps 46 is detailed in FIGS. 6 and 7, this having the advantage that straps 46 can be assembled under predetermined longitudinal tensions, which can be particularly desirable in installations where there exists considerable transmitted vibrational stress from adjacent plant equipment, such as reciprocatory compressors or the like. In this case, an exceptionally tight tube assembly is essential in order to insure that invariant air passages are always maintained throughout the tube bundles.

The alternate design dispenses with channels 5% and substitutes I-beams 49 which are slotted on the inboard flanges at 78 to receive the ends of the straps, again provided with longitudinal slots 66, which then overlie the web portions 49 of the Lbeams. The outer edges of the slotted ends of the straps are cut away to form notches 79 which receive oppositely disposed C-profile spring clamps 80, brought into tight abutment at the top edges against the undersides of the inboard flanges of l-bearns 49 and at the bottom edges against the lower ends of notches 79 by tightening the nuts 81 on bolts 82 threaded at both ends and passed through drilled holes in web 49. It will be understood that an identical construction is employed on the other ends of straps 46, making it possible to effect tension adjustment at will from either side of the tube bundles.

Regardless of which design is employed, straps 46 apparently cross-brace finned tubes 33 in tight rigidity, which enables tilting of the assembled tube bundles into any plane without alteration in tube position.

It is sometimes desirable, as an aid in the assembly, to support individual tubes in temporary position at preselected points farther apart that the 4 span intervals which are preferred for the heat exchanger tube bundle of FIG. 1, and the apparatus of FIGS. 8l1 has been devised for this purpose. Here a strap 46" identical in all respects with straps 46 hereinbefore described, except with the modifications now to be detailed, is employed solely for assembly purposes.

Strap 46 is notched along both edges as indicated at 85 in the root portions of the undulations so as to receive U-pieces 86, which are proportioned to just abut the crests of the opposed undulations on the strap 4-6 disposed to the right, thereby affording a temporary base for support of the finned tube thereabove. It is contemplated that straps 46" and their U-pieces 86 will be employed at alternate intervals of, for example, every 8' apart over the tube bundle length, thereby alfording support and location to individual tubes while they are being rolled in or otherwise attached to their headers. Thereafter, when the final straps 46 are put into place, these are first assembled in the alternate vacant positions existing between straps 46". Then the latter are pulled and replaced by regular straps 46, bringing the assembly to completion.

For purposes of the description, a tension bar 69' is shown in FIG. 10 in conjunction with notched end straps 46 and 46''.

While substantially horizontally disposed finned tubes 33 have been hereinbefore specifically described, support straps 46 can be fabricated in slightly twisted edge-to-edge slopes, so as to furnish a slight progressive downward inclination throughout successive rows of tubes insuring gravitational liquid flow therethrough, if this is desirable. Accordingly, the term generally horizontal, as used in the claims, is intended to comprehend. also tubes slanted enough to be self-draining.

A very important advantage of the construction is that support straps 46 are sufiiciently springy so that, when disengaged from slots 60 at one end, they can be deflected laterally a sufficient amount to permit removal of a defective tube from anywhere within the tube bundles with the prior disengagement of only a few overlying tubes being necessary to open the way. This is made possible by the relatively shallow cradle portions of the straps abutting the finned tube peripheries, which readily free the tubes from restraint when straps 46 are temporarily bent aside.

From the foregoing it will be apparent that this invention can be modified in numerous respects within the skill of the art without departure from its essential spirit, and it is accordingly intended to be limited only within the scope of the following claims.

What is claimed is:

1. In an air-type heat exchanger comprising a rigid external framework, inlet and outlet process fluid headers connected at opposite ends in the process fluid flow path with a tube bundle disposed within said. framework in inclined relationship with respect to the horizontal, said tube bundle being made up of a multiplicity of finned tubes having a length-to-diarneter ratio above about 200, said tubes being disposed in generally horizontal superposed planes, demountable tube support means aligned one with another across said bundle carrying substantially the full weight of said tubes individually disposed longitudinally between said inlet header and said outlet header, generally transverse rows of said tubes lying in a common substantially horizontal plane within said tube bundles, said tube support means consisting of a unitary strap bent in a repetitive undulatory pattern intermediate the ends to provide a sucession of shallow, arcuate concavities abutting the peripheries of said tubes, and support mem bers fixedly attached to said framework receiving the ends of said straps in weight-supporting relationship.

2. Apparatus according to claim 1 wherein said arcuate concavities are formed on circular radii approximately equal to the outside radii of said finned tubes and are of an expanse encircling said finned tubes throughout an angle ranging from about 15 to about 75 measured on the periphery of said finned tubes.

3. Apparatus according to claim 1 wherein said arcuate concavities are formed on a sinusoidal pattern of amplitude receiving said finned tubes to a depth up to approximately 25% of the radius of said finned tubes.

4. Apparatus according to claim 1 wherein said de mountable tube support means are provided at the ends with longitudinal tensioning means locking said finned tubes in tight, substantially invariant relationship with respect to one another.

References Cited UNITED STATES PATENTS 2,402,209 6/1946 Ryder -463 2,927,781 3/1960 Fohrhaltz et a1 165-69 3,139,070 6/1964 Sprague et al. 122-34 3,163,208 12/1964 Cuzzone et al 165-69 FOREIGN PATENTS 685,848 1/1953 Great Britain.

ROBERT A. OLEARY, Primary Examiner. M. A. ANTONAKAS, Assistant Examiner. 

